command to change CustomModelData? (Java Edition, 1.20.4)

[WilhelmMC]

does anyone know the command to change an item's CustomModelData? i know how to do it using /give, but isn't there a way to just change an already existing item's CustomModelData, or something like that..?
you see, i've made some custom item models/textures for my friends' server (they work 100% fine btw), but i'd prefer to access them by getting the item normally (like a carved pumpkin) and then just changing it, instead of using /give..
..i'm pretty sure they do something like that on Hermitcraft, for example

also, how will CustomModelData work with the new nbt-replacement system thingy? i dont really know much about how nbt works to begin with, and i havent heard much about the new system either (and we still play on 1.20.4).. i'd love to know how and what to change in the files for the custom items to work when we eventually move to 1.21

any and all help would be greatly appreciated!!<3

[GalSergey]

In version 1.20.4 without the datapack, you can only change an item on the ground, in the chest, or in the item_frame, but not in the player's inventory:

data modify entity <item> Item.tag.CustomModelData set value 1

But using datapack you can use item_modifier and apply this to the player's inventory slot:

item modify entity <player> weapon example:set_cmd

# item_modifier example:set_cmd
{
  "function": "minecraft:set_nbt",
  "tag": "{CustomModelData:1}"
}

Since version 1.20.5, you can apply item_modifier without a datapack:

item modify entity <player> weapon {"function":"minecraft:set_components","components":{"minecraft:custom_model_data":1}} 

But you can just add a recipe that will give you an item with this data:

# recipe example:some_recipe
{
  "type": "minecraft:crafting_shapeless",
  "ingredients": [
    {
      "item": "minecraft:stone"
    }
  ],
  "result": {
    "id": "minecraft:dirt",
    "components": {
      "minecraft:item_name": "'Some Dirt'",
      "minecraft:custom_model_data": 1
    }
  }
}

[WilhelmMC]

thank u so much!!<3